Telephone repeating system



M. LATOUR TELEPHONE REPEATING SYSTEM Filed April 28 192$ SECOND/JE/ZS OF/LCSOUECE T A. r

.SECO/VDAE/Ej OF A .C. SOURCE To all whom it may concern:

Patented did 11?,

t at we maroon, or rears, memos.

Application filedhpril 28, 1923. Serial No. 685,280.

Be it known that" I, Memos La'romz, a citizen'of the Republic of France, residing at Paris, France, have invented certain new and useful Improvements in Telephone Re- ,p' a inglsystems st tor which I have filed an I iipplicat'ionin France; on April 22, 1922,

specification.

The resent invention-relatesto improve- 111811198 111 two-way amplifyin "systems as applicable to interurban te e, onic commumcation-and isrmoret particu arly described with-- reference to the accompanying diagrammatic drawings 1 to 3 inclusive.

' Figure 1 illustratesthe principle of operation of the invention as applied to link a four-wire interurbanline with a two-wire subscr bers line at each of its extremities.

former. a

In Figure 1' the interurban line is represented by the two pairs of conductors 1, 2,

each comprising a unilateral amplifyingrelay R R respectively, serving to amplify the microphonic currents in the directions indicated by the arrows. A subscriber7s instrument comprising a 'telephone receiver 6, an induction coil 7 a.

microphone 8 and a cell 9, is connectedtov one-extremity of-the interurban line through a vibrator 5 which alternately makes contact with the line teals 3 and 4. A similar subscribers instrument is connected to the other extremity of the interurban 1 line,

through a vibrator 5'. which alternately makes contact with the line terminals 3" p and a.

In Figure 1, similar numbers denote ilar organs, the ri ht-ha'nd numbers being I afiected with an in ex merel' to difierentiate the relative positions of t e organsv with reference tothe interurbanline.

If we consider the vibrator reeds 5 and 5 as bein respectively in. contact with the "'termina 's 3 and 3, it is obviousthat the teleephone receiver 6 .willbc" traversed by the speech currents by themicrophonc 15,867), of, which:the following is a 8 and amplified in transit through the amplifying relay R Reciprocally, if we consldcr the vibrator reeds 5 and 5 as being respectively in contact with the terminals 4: and 4', it is obvious that the receiver 6 will "be traversed by the speech currents emitted by the microphone 8 and amplified in transit through the amplifying relay R If the vibrators!) and 5' operate synchronically -a coherentcommunicat'ion may be establis ed between the twoextrem'e subscribers providing the vibrators operate ata sufficientlyv high frequency. It is seen that this system amounts to having aiunilateral amplifying repeater the direction of which is rapidly alternated.

The-synchronous operation of both' vibrators could be arrivedat by means of a special arrangement, but in view of the electrostatic capacity of the telephone line,

vwhichline is usually a long distance cable, this s nchronism need not be established as the e ectrostatic capacity'delays the effective charge produced upon the conductors by the current passing through the closed vibrator until the other vibrator Becomes effective. pacity being insuflicient, additional condensers may be branched at the extremities of the interurban line.

In Figure 1, the vibrators 5 and 5' are indicated merely by way of example and the present invention does not purpose to restrict itself to the'exclusive use of vibrators of the type described.

' Figure 2 illustrates the present invention in its most elaborate form. this form, the arrangement represented therein is inserted between each subscribers two-wire line and'the corresponding extremity of the.

four-wire interurban line described with reference to Figure 1. In accordance with the invention, the commutating action 'of the vibrator described above is obtained by means of two thermionic tube relays of the con u- Inev-ent of the inherent line cagated type theanodc circuits of which are su plied with alternating current.

in Fi re 2, the subscribers line A is branche to the primarywinding 1 of the subscribers input transformer the secondary winding 2 of which is connected to the grids of tubes3 and 4 in such summer as to bring each grid to a potential opposite in si' with reference toea'ch other. The subscribersoutput transformer prry ,7 is inserted inthe anode circuits too I of tubes3and 4 in such a manner. as thereresults, at an instant, no induced current in .coil 8' prov ding the anodes of tubes3 .and

'4 take equal currents. -Under these conditions, the secondary winding 8 of the subscribers output transformer can only give rise to amplified telephonic currents which are sent on to one pair of conductors L of the four-wire interurban line. The terminals of the other pair of interurban line conductors L are connected to the prim'ary winding 1 of the line input transformer "the. secondary winding2' of which is concircuits of tubes 3'. and 4' in such a manner as there results, at any instant, no induced current -in coil 8 providing the anodes of tubes 3' and 4 take'eqnal currents.

The cathodes of the left-hand set. of tubes are brought to incandescence by means of a bathe The anode circuits of both sets of ther- Il "mionic tube relays are supplied with-alternating current from the secondary windings 6, 6' of a supply. transformer, or by any other appropriate alternating current genen' ator, in-such a manner as to have, at any instant, each set oianodes subjected to a voltage opposite in sign with reference to each other Y Under these conditions, it will be seen that, at any instant,,there is only one set of tubes which is'in an operative condition. This is equivalent to the action of the vibrator of Flgure 1 in which the. subscribers Iine'is alternately branched onto the output and input pai s of the interurban'conductor's. In

order shorten, during each half cycle," the length of time during which each .setof anodes is subjected to. positive potential, a

source of direct, current may be inserted in each'cathodelead. In Fig.4 I have shown suchmodificatiom A source ofdirect'current is located in each cathode lead from the secondary winding 6 andfi'.

If it is des'red o obtain fication ordinary unilateral amplifiers may i be inserted between thc subscri rfs output transformer secondary winding 8 and its a: rresponding line terminals L 01' b f the line input transformer primary naeege ce The line-output transformer primary winding? is inserted in the anode terminal ampli-.' alternately branch said subscribers lineto" 1" and its corresponding line terminals L" having due regard to the direction of amplification. I

If we do not take the electrostatic'capacity of the telephone line into account, it is clear that the working of this system can only become eff cient as starting from an anode circuit feedin current fre uency vof about 2000 cycles. 11 view of this line capacity however, we may advantageously shorten,.

during eachhalf cycle, the. length of time during which each set of anodes is subjected to positive potentialby inserting a source of direct current in the cathode lead of each winding 6, 6', as described above. This a'r rangement has the ad vantage of facilitating reduction in the feeding current frequency Figure 3 illustrates the commutating arrangement of Figure 2 operated as a two- I way repeating amplifier inserted at some in termedlate point of an ordinary two-cone ductor interurban line. In Figure 3 and in Figure 2, similar numbers are used to designate similar organs. The operation of the 5., those of the right-hand set being 'heate byia similar battery arrangement described'in Figure 3 is similar to that of a unilateral repeating amplifier the direction of 'whichds rapidly alternated.

What I claim and desire to secure by United States Letters Patent is:

1.- In an interurban telephone 'communication system, a transmission line consisting airs of speech conducexclusively of two tors, each pair inclu ing a uni-lateral amplifying repeater, a two-conductor subscribers am liiying repeater, a two-conductor subscri er s nected pairs of balanced thermionic tube relays supplied with .alternat' current to either pair of interurban conductors.'-

2. interurban telephone communication 2 system consisting or two pairs of interurban conductors, each pair including a uni-lateral line at each extremity of the fourwire mterurban line, and two sets of con- I testimony'whejreof I afli'x my signature. i

- rUsLA'ro R. 

